A charger for an electric power tool has been in general configured to notify a user of a power connection state where the charger is connected to an external power source, a charging state where a secondary battery mounted therein is being charged, a charging completion state where the charging has been completed, and the like by using a light emitting member, e.g., a light emitting diode (LED).
A charging time needed to charge a secondary battery varies depending on the capacity and type of the secondary battery. The charging time typically ranges from about 15 minutes to about 60 minutes or more.
For that reason, it is important to a user to notify of the charging completion state. Accordingly, there has been developed a conventional charger having, e.g., two different color LEDs which notifies the user of various operation states until the charging is completed by using combinations of turn-on and turn-off of respective different color lights of the LEDs (see, e.g., Japanese Patent Application Publication No. 2004-173376 and corresponding US Patent Application Publication No. 2004-0135548 A1).
Further, there has been developed another conventional charger that notifies the user of various operation states by changing a current supplied to an LED therein to thereby change brightness of the light emitted (see, e.g., Japanese Patent Application Publication No. 2008-236880 and corresponding US Patent Application Publication No. 2008-0231229 A1). For example, the charger gives a user a notification of the charge completion state by supplying a current larger than that for other notification to the LED so that the LED emits light brighter than other notifications to thereby make the user recognize the charge completion state easily.
However, all the above-described chargers notify an outside world of the charging states by emitting the light without varying brightness regardless whether or not there is a user around the chargers.
In other words, such conventional chargers allow their notification units to continuously emit lights to give a notification to an outside world during the long-term charging period of a battery even when the notification becomes unnecessary due to the absence of a notification target, e.g., a user around the chargers. Accordingly, the power is wasted by the notification units.